Roadmap for Optical Tweezers 2023

Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration

Acoustic Waves

The concept of acoustic wave is a pervasive one, which emerges in any type of medium, from solids to plasmas, at length and time scales ranging from sub-micrometric layers in microdevices to seismic waves in the Sun's interior. This book presents several aspects of the active research ongoing in this field. Theoretical efforts are leading to a deeper understanding of phenomena, also in complicated environments like the solar surface boundary. Acoustic waves are a flexible probe to investigate the properties of very different systems, from thin inorganic layers to ripening cheese to biological systems. Acoustic waves are also a tool to manipulate matter, from the delicate evaporation of biomolecules to be analysed, to the phase transitions induced by intense shock waves. And a whole class of widespread microdevices, including filters and sensors, is based on the behaviour of acoustic waves propagating in thin layers. The search for better performances is driving to new materials for these devices, and to more refined tools for their analysis

Stimuli-Responsive Nanoparticles for Bio-Applications

Stimuli-responsive nanoparticles have been designed and studied, exploring their potentiality as self-assembled materials as building blocks for the development of "smart" materials for bio-applications. Perylene diimide derivatives (PDI) have been used as fluorogenic units and structural components of assembled high-brightness nanoparticles, where fluorescence changes can be triggered by external (light) or internal (pH) stimuli which promote disaggregation induced emission (DIE). Synthesis of PDI (P) was achieved by microwave heating in mild conditions. π-π stacking and inter-substituent interactions drove the self-assembly of quenched nanoparticles that were internalized by yeast cells responding as fluorogenic imaging agents. By controlling the dosage, they displayed either green or red fluorescence. Multicolour fluorescence imaging was achieved by sample photo-activation under strong light irradiation. P was adopted as structural component of covalently linked nanoparticles. P chains have been cross-linked by an epoxy monomer into Pluronic micelles, driving the formation of core-shell nanoparticles. Vicinity of the monomer aromatic regions caused the quenching of the emission, which could be recovered by fluorophore disaggregation triggered by light irradiation in proper conditions of concentration and/or polarity. Photo-activation occurred also after nanoparticles internalization by living cells, confirming the possibility of using them as stimuli-responsive fluorogenic bio-imaging agents. Fluorogenic pH-responsive nanoparticles have been further designed and developed, with the purpose of differentiate normal and cancer tissues. A monodispersed amphiphilic block co-polymer, constituted by a PEGylated hydrophilic block and a tertiary amine pH responsive hydrophobic block, functionalized by a PDI norbornene monomer, was synthesised by ring opening metathesis polymerization. Polymer self-assembly was exploited to obtain spherical core-shell nanoparticles, quenched in neutral pH thanks to the π-π stacking in the nanoparticles core. By switching the pH from 7.4 to 5, structural modification in the hydrophobic block were promoted, leading to the nanoparticles disassembly and to the recovery of PDI emission

Laboratory directed research and development. FY 1995 progress report

This document presents an overview of Laboratory Directed Research and Development Programs at Los Alamos. The nine technical disciplines in which research is described include materials, engineering and base technologies, plasma, fluids, and particle beams, chemistry, mathematics and computational science, atmic and molecular physics, geoscience, space science, and astrophysics, nuclear and particle physics, and biosciences. Brief descriptions are provided in the above programs